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USEPA / Stormwater-Management-Model

Dynamic hydrology-hydraulic water quality simulation model
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Flap gate losses #201

Open MitchHeineman opened 4 weeks ago

MitchHeineman commented 4 weeks ago

Discussed in https://github.com/USEPA/Stormwater-Management-Model/discussions/170

Originally posted by **MitchHeineman** April 16, 2024 SWMM inherently applies the Armco equation for losses across flap gates associated with weirs and orifices. However, unless I'm not looking closely enough, it does not assign comparable losses to flap gates on pipes or outfalls. This seems inconsistent to me. While the user can apply a form loss coefficient to the pipe above an outfall or to a pipe with an internal flap gate, that's a slightly different equation.
MitchHeineman commented 4 weeks ago

A bit more information... The inconsistency appears to date to at least SWMM4 which includes the Armco equation for weirs (bound.for), but not orifices. The term was added to orifices in SWMM5 (link.c). I suspect the original addition in 4 was to meet a specific need, and no one has ever considered the issue of consistency across different types of tide gates, no less the various places one can represent a gate in SWMM (orifice, weir, pipe, outlet, outfall)